Patent Literature 1 discloses a configuration of a conventional reflection-type optical position transducer system. FIG. 13A to FIG. 13E are diagrams for explaining the reflection-type optical position transducer system. FIG. 13A to FIG. 13E respectively show an illustrative schematic isometric view of the position transducer system, an illustrative schematic isometric bottom view of a reflector element in the position transducer system, an illustrative schematic plan view of a light source and a detector circuit of the position transducer system, an illustrative schematic bottom view of the reflector element, and an illustrative schematic side section view of a rotation restriction motor system.
The conventional reflection-type optical position transducer includes a single LED light source 26, a reflector 12 attached to a rotating shaft of a rotation restriction motor and alternately having regions providing specular reflection and regions providing illumination absorption, and a detector 14 that receives reflected illumination light from the reflector. The reflector 12 is attached to the upper end part of a rotator shaft 30 that rotates within a housing 32. On the surface of the reflector 12 facing the detector 14, three specular reflection regions 16 and three illumination absorption regions 18 are formed and disposed alternately. In the detector 14, the single LED light source 26 is disposed at the center, a light shielding unit 28, such as an O-ring, is attached on the periphery thereof, and further three pairs of detector regions 20a and 20b, 22a and 22b, and 24a and 24b are provided on the periphery of the light shielding unit 28. Light emitted from the single LED light source 26 is reflected by the specular reflection regions 16, and received by the detector regions 20a and 20b, 22a and 22b, and 24a and 24b. The received light output is processed in a processing circuit.
Patent Literature discloses a structure of an optical system of an optical rotary encoder. The encoder includes a light source, a rotary scale, a reflector, and a light-receiving element. The light source is provided in the vicinity on the rotation center line of a rotating shaft. The rotary scale is attached to the rotating shaft so as to be capable of rotating about the rotation center line, and has an optical pattern including light-transmitting parts and light shielding parts formed alternately in the circumferential direction. The reflector is disposed with an interval from the rotary scale, and reflects light from the light source so that the light forms a parallel light flux whose width almost does not change within the section including the rotation center line, and thereby, the parallel light flux illuminates the light-transmitting parts of the rotary scale and the light having passed through the light-transmitting parts travels toward the periphery of the light source. The light-receiving element receives the light having passed through the light-transmitting parts. The optical rotary encoder according to Patent Literature 2 is a transducer that detects bright and dark light from the reflector by a detector, encodes the light in a circuit in the subsequent stage, and thereby obtains position information.
Patent Literature 3 relates to an encoder as in Patent Literature 2, and discloses an optical system that utilizes a reflective cylindrical surface. In this encoder, a module including a photo-detector and a light source is disposed to face a drum. On the surface in the circumferential direction of the drum, stripe-shaped non-reflection regions are provided at regular intervals. The drum is illuminated with light of the light source, and the light reflected thereby is detected by the photo-detector. Patent Literature 3 discloses an optical system and a detection method unique to an encoder that illuminates non-reflection regions disposed in the form of a stripe on the surface of the drum and the reflection regions therebetween with light, and that detects the rotation position of the non-reflection regions by reflected light.
Patent Literature 4 discloses a structure of a rotary motor for detecting a rotation position. In this rotary motor, in order to detect the rotation position thereof, a butterfly-shaped diffusion surface having an angle width of 90 degrees is attached to a rotor shaft. The diffusion surface has an opaque surface in the shape of a disc in the vicinity of the central part (see Patent Literature 4, FIG. 1B). A lens is disposed to face the diffusion surface, and behind the lens, a stationary detector is installed. As a light source, four LEDs are disposed on both sides of the lens. Light emitted from the four LEDs is reflected by the rotating diffusion surface, and the reflected light is concentrated by the lens and received by the stationary detector. In the rotary motor in Patent Literature 4, the LEDs and the detector are disposed not on the same plane but in different spaces, and from each of the four LED light sources, light is illuminated toward each of the reflection surfaces.